1. Field of the Invention
The present invention relates to an electron emission device and an electron emission display using the same, and more particularly, to an electron emission device and an electron emission display, in which a driving electrode is protected from being damaged when an overcurrent instantly flows therein.
2. Discussion of Related Art
Generally, an electron emission device is classified into a hot cathode type or a cold cathode type, wherein the hot cathode type and the cold cathode type employ a hot cathode and a cold cathode, respectively, as an electron emission source.
A cold cathode type electron emission device includes a structure such as a field emitter array (FEA), a surface conduction emitter (SCE), a metal insulator metal (MIM), a metal insulator semiconductor (MIS), a ballistic electron surface emitting (BSE), etc.
The electron emission device having the FEA structure is based on a principle that a material having a low work function and a high β-function is employed as an electron emission source and emits electrons due to electric field difference in a vacuum. Such an FEA electron emission device includes the electron emission source having a sharp pointed tip and made of a carbon material or a nano material.
The electron emission device having the SCE structure is provided with an electron emission portion, in which two electrodes are opposite to each other and formed on a plate and a conductive layer is formed between the two electrodes, wherein the conductive layer is formed with a minute crack or gap, thereby forming the electron emission portion. Such an SCE electron emission device is based on a principle that the electron emission portion formed by the minute crack or gap emits electrons when voltage is applied between two electrodes and an electrical current flows through a surface of the conductive thin layer.
The electron emission device having the MIM or MIS structure includes an electron emission portion having a metal-insulator-metal structure or a metal-insulator-semiconductor structure and is based on a principle that electrons are emitted from a metal or a semiconductor of high electric potential and accelerated toward a metal of low electric potential when a voltage is applied between the metal and the metal or between the metal and the semiconductor.
The electron emission device having the BSE structure is based on a principle that electrons travel without sputtering when the size of a semiconductor is smaller than a mean free path of the electrons contained in the semiconductor. Such a BSE electron emission device includes an electron supplying layer made of a metal or a semiconductor and formed on an ohmic electrode, an insulator formed on the electron supplying layer, and a thin metal layer formed on the insulator, so that the electrons are emitted when a voltage is applied between the ohmic electrode and the thin metal layer.
The foregoing electron emission devices are employed in an electron emission display, various backlights, an electron beam for lithography, etc. In the case of the electron emission display, there are provided an electron emission device including an electron emission region for emitting electrons, and an image-displaying region in which the emitted electrons collide with a fluorescent layer and thus emit light. Generally, an electron emission display includes a plurality of electron emission devices formed on a first plate, a driving electrode for controlling the electron emission devices to emit the electrons, and a fluorescent layer and an electrode connected to the fluorescent layer to efficiently accelerate the electrons toward the fluorescent layer.
However, in the foregoing electron emission display, a distance between the driving electrodes or a distance between the driving electrode and the electron emission portion is just a few μm through a few scores of μm, so that they are likely to be short-circuited by foreign material or arcing. To solve this problem, various devices have been proposed. For example, there is a conventional electron emission device disclosed in Korean Patent No. 10-289638.
FIG. 1 is a plan view that schematically illustrates a conventional electron emission device, and FIG. 2 is a cross-sectional view of the conventional electron emission device, taken along the line A-A in FIG. 1.
The conventional electron emission device of FIG. 1 includes a plate 1, a cathode interconnection line 2 formed on the plate 1, an island electrode 3, first and second resistive layers 4 and 5 formed on the island electrode 3 in sequence, a gate electrode 8 insulated from the second resistive layer 5 by an insulating layer 6, and a micro tip 7 connected to the first resistive layer 4 and formed within an opening of the insulating layer 6.
In this electron emission device, the first and second resistive layers 4 and 5 are different in resistance from each other and layered as shown in FIG. 2. Hence, when an overvoltage is applied to the micro tip 7, the layered structure of the first and second resistive layers 4 and 5 is likely to be broken off, thereby isolating the island electrode 3 from the cathode interconnection line 2. That is, when the gate electrode 8 and the micro tip 7 are short-circuited, the short-circuited, it is possible to separate only the island electrode 3 electrically connected to the micro tip 7 from the cathode interconnection line 3.
However, the conventional electron emission device has a relatively complicated structure, so that production cost thereof is relatively high and it still has a problem in reliability.